Orc

An orc, in mythology and fantasy, is a race of humanoid creature akin to goblins. The word "orc" comes from Orcus, the Roman god of death, and they are generally ugly and filthy, bearing a mixture of ape-like and pig-like grotesque facial features (including fangs), while their skin colors can be green, grey, black, brown, or sometimes red or sandy tan.

Azerothian mythology
In Azerothian mythology, Orcs originally hailed from the world of Draenor, but the majority of clans were tricked into serving a force of world-destroying demons, the Burning Legion. The Orcs slaughtered their Draenei enemies and were mystically transported to the world of Azeroth to conquer it in the Legion's name, with the Fallen Titan Sargeras possessing the prophet Medivh and forcing him to open the "Dark Portal" into Azeroth. After two devastating wars, the Orcs were defeated by the human Alliance and rounded up into internment camps. They remained there until the human-raised orc Thrall rallied them together, freed the Horde from the influence of the demons, and founded a new Horde on the principles of strength and honor. The Horde broke free from human captivity and was sent to Kalimdor by Medivh in 25 ADP (After the Dark Portal), where they were to assist the humans in fighting off the Burning Legion. Under Medivh's guidance, Thrall and Alliance leader Jaina Proudmore put aside their differences, and they allied with the Night Elves before defeating the Burning Legion at the Battle of Mount Hyjal and destroying Archimonde, the Burning Legion Lord.

The Orcs would become the most important Horde faction in the following decades, and the Horde and Alliance has several skirmishes, although they would not enter all-out war until Garrosh Hellscream (son of the great Horde leader Grom Hellscream) became Chief. His warmongering led to a civil war in the Horde, with Vol'Jin of the Trolls leading a rebellion against Garrosh. Garrosh was ultimately killed in a duel with Thrall, and Vol'jin would become the new Horde leader.